1. Field of the Invention
The present invention relates to a valve assembly for sealing an opening in a processing system. More particularly, the invention relates to a valve assembly which prevents exposure of the seals incorporated in the valve assembly to the process environment.
2. Background of the Related Art
In the fabrication of integrated circuits and flat panel displays, various processing chambers and systems are employed to perform multiple deposition and etch processes on substrates to form electronic devices. Examples of some processes include chemical vapor deposition, physical vapor deposition and various etch processes performed in processing systems using volatile and corrosive gases. The corrosive gases typically attack the exposed chamber components including o-ring seals found in valves disposed in exhaust lines connecting vacuum pumps to the processing systems.
FIG. 1 is a schematic cross sectional view of a processing chamber 100 showing a chamber body 110 housing a substrate support member 112, and having a gas distribution assembly 113, a turbo pump 115 (or some other high vacuum pump) located below an exhaust outlet 114, and a by-pass line 116. One or more valves 118 are typically disposed on an exhaust line 117 and the by-pass line 116 to control chamber pressure during processing and to stabilize the system when a substrate is not positioned for processing. A slit valve assembly 120 selectively opens and closes an aperture 122 through which substrates are transferred.
Typically, gate valves or other type valves 118 disposed in the exhaust lines 117 and by-pass lines 116 have exposed o-ring seals when the gate valve is in the open position. As a result, the volatile and corrosive gases contact the seals. The seals currently used are susceptible to attack from these gases and continual exposure requires frequent replacement of the seals, resulting in increased operating costs and decreased throughput.
Therefore, there is a need for a valve assembly that prevents exposure of the valve seals to the corrosive gases during operation of the valve.